1. Field of Invention
The present invention relates to a liquid crystal device, a method for fabricating the liquid crystal device, and an electronic apparatus including the liquid crystal device. More specifically, the invention relates to a technique of disposing spacers between substrates.
2. Description of Related Art
A related art liquid crystal device has a structure in which a lower substrate and an upper substrate are bonded together along the respective peripheries thereof, having a sealing member interposed therebetween at a predetermined gap, and a liquid crystal layer is hermetically filled between the pair of substrates. Also, a related art liquid crystal device has an exemplary structure in which a lower substrate has a color filter layer, which includes red, green and blue coloring layers, and a light-shielding layer (a black matrix), and a protective layer to protect the color filter layer, sequentially formed thereon, and in addition, the lower substrate has transparent electrodes formed in a striped array on the protective layer. An upper substrate has other transparent electrodes formed thereon in a striped array, and both transparent electrodes have respective alignment films formed thereon.
In such a liquid crystal device, a large number of spherical spacers are disposed between the substrates, each substrate having the corresponding transparent electrodes and alignment films formed thereon, in order to make the gap between the substrates uniform across the surfaces of the substrates. One of two related art methods of disposing such spacers between the substrates is a wet scattering method with which a spacer-dispersed solution prepared by dispersing the spacers in a solvent such as water, chlorofluorocarbon, isopropyl alcohol, or ethanol is sprayed with gas such as air or nitrogen so as to be scattered on the surface of either of the substrates; and the other is a dry scattering method with which the spacers get electrically charged spontaneously or by some artificial method while being supplied with a carrier gas such as air or nitrogen and are accreted on either of the substrates due to the electrostatic forces thereof. In such wet and dry scattering methods, since the spacers are scattered on either of the substrates due to the free fall thereof, it is difficult to control the scatter positions of the spacers; as a result, sometimes the following problems take place.
For example, when spacers are partly aggregated in some locations in a liquid crystal device, and thus the distribution density of the spacers becomes nonuniform, the variance of gaps between the substrates sometimes becomes larger. Also, in the case of a liquid crystal device of an active-matrix type, since switching elements and the like for driving the transparent electrodes are formed on the substrates, steps are produced on the surfaces corresponding to the regions where elements have been formed. When the spacers are scattered on such regions having the steps formed therein, the variance of gaps between the substrates sometimes becomes larger.
When the variance of gaps between the substrates becomes larger as described above, the variance of thickness of a liquid crystal layer (the cell thickness) sandwiched therebetween becomes larger. Thus, when the liquid crystal device is used as a display device, the large variance of cell thicknesses causes display performance of the display device to be deteriorated.
In particular, in the liquid crystal display in an STN (super twisted nematic) mode, the transmittance of light varies as the value of Δn·d varies (where, Δn: double refractive index of liquid crystal, d: cell thickness). Accordingly, large variations in values of Δn·d, that is, large variance of the cell thickness d causes large variations in light transmittances and thus color unevenness of display to occur, whereby the quality of display sometimes deteriorates. In order to reduce the forgoing variance of cell thicknesses, for example, Japanese Patent Laid-Open No. 2001-222015 discloses a technique with which, corresponding to projections formed on the substrate, depressions are formed on a counter substrate.